Serpentine tube inspection positioning spine

ABSTRACT

A serpentine tube inspection positioning spine formed from a plurality of identical links mated together. Each link has first and second bifurcated ends with the first end sized to fit within the second end of an adjacent link. Links are mated together by a pivot pin or axle which is accepted in a bore through the bifurcated ends. The second bifurcated end is provided with a substantially oval-shaped bore to allow sliding of the adjacent links relative to each other. Flat alignment faces on each end, with the first end having rounded corners, prevent buckling due to compressive forces during insertion while still allowing pivoting of the links for traveling through tubing bends.

This application is a division of application Ser. No. 07/260,161, filedOct. 21, 1988 now U.S. Pat. No. 4896555.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to non-destructive inspectionof pipes and tubing and in particular to positioning of inspectiondevices at various locations along the interior of serpentine-bent tubesections.

2. General Background

Many boilers have serpentine-bent horizontal tube sections. Such tubesections are generally of a 1 to 2 inch inner diameter with multiple (asmany as 20) tight radius 180 degree bends and may be several hundredfeet long. Non-destructive testing of the interior of the tubing isaccomplished by the use of transducers. The type of mechanism used tomove a transducer through a tube is chosen depending on tube diameter,the number, direction, extent, and radius of bends, and the length ofthe tube to be inspected. Moderately short lengths of tubing with fewand gradual bends often depend upon a flexible cable similar to aplumber's "snake" for movement of an inspection transducer. Such devicesare not known to be applicable to boiler tubes as described above."Tractor" devices capable of negotiating the sharp bends and pulling atransducer and its signal cable along are also not known. Flexiblecables pushed from the end of the tube are impractical beyond the firstor second bend in the tubing due to the build up of drag forces. Variousdevices of which the inventors are aware include the following.

U.S. Pat. No. 3,583,393, No. 3,497,083, and No. 4,238,973 discloseselectively bendable tube assemblies and manipulators.

U.S. Pat. No. 2,748,803 and No. 4,648,733 disclose a reinforced hose andinstallation template for conduits.

U.S. Pat. No. 3,623,756 and No. 3,918,821 disclose articulatedconnectors.

U.S. Pat. No. 4,290,762, No. 3,020,362 and No. 3,197,954 disclosevarious link chains.

Although a variety of flexible connectors are available, none fit theneed to be able to travel through serpentine tube sections as describedabove wherein the device must be capable of being pushed through thetubes and then pulled back out once inspection is completed.

The problems encountered are as follows. During insertion, when thedevice is being pushed through the tube, compression forces result inthe links having a tendency to buckle at the link connecting pivotpoints, causing lock-up in straight sections of the tube and generatingside loads that quickly become unacceptably high. Major drag forces arealso generated in the bend areas of the tube during insertion andremoval of known devices.

SUMMARY OF THE INVENTION

The present invention solves the aforementioned problem in astraightforward manner. What is provided is a positioning spine formedfrom a series of rigid links. Both ends of the links are bifurcated andsized such that a first bifurcated end of one link is received withinthe second bifurcated end of an adjacent link. Coaxial bores areprovided in each projection of the bifurcations and receive an axlewhich joins adjacent links together. Wheels mounted on the axles allowrolling movement of the spine through the tubing with a minimum offriction. Separate alignment faces are provided on the first bifurcatedend of each link along with the capability of the links to slidelongitudinally relative to each other. This combines to allow limitedpivoting of the links relative to each other for traveling through atight radius bend while maintaining alignment of the links in thestraight portions of the tubing.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the presentinvention, reference should be had to the following description taken inconjunction with the accompanying drawings, in which like parts aregiven like reference numerals and, wherein:

FIG. 1 is a schematic view of the invention in a tube section.

FIG. 2 is a side view of the invention.

FIG. 3 is a top view of the invention.

FIGS. 4, 5 and 6 illustrate alternate embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, it is seen in FIGS. 1-3 that the invention isgenerally referred to by the numeral 10. Positioning spine 10 isgenerally comprised of a plurality of rigid links 12 and wheels 14.

As best seen in FIGS. 2 and 3 links 12 are identical and of a generallyrectangular configuration. Each link has first and second bifurcatedends 16, 18 which extend outwardly from central link portion 20 alongthe longitudinal axis thereof. As best seen in FIG. 3, first bifurcatedend 16 is narrower than central link portion 20 and sized to slidablyfit within second bifurcated end 18. First bifurcated end 16 is providedwith bore 22 therethrough perpendicular to the longitudinal axis. Meansfor preventing buckling of the mated links during insertion andmaintaining rigid straightness when under compressive forces is providedin the form of flat alignment faces on the bifurcated ends.

First bifurcated end 16 is provided with flattened end face 24perpendicular to the longitudinal axis of link 12. Second bifurcated end18 is provided with flat inner faces 26 which correspond to flattenedend faces 24. It can be seen that during compression (insertion ofpositioning spine 10 into tube 27) alignment and contact between flatfaces 24 and 26 of adjacent links serves to resist any tendency towardbuckling between links, thus maintaining rigid straightness ofpositioning spine 10 in straight portions of the tube.

Means for allowing pivoting of one link relative to an adjacent link fortraveling through a tubing bend is also provided. Flattened end face 24is provided with rounded corners 28. Second bifurcated end 18 isprovided with bore 30 which is substantially oval shaped andperpendicular to the longitudinal axis of link 12. Pivot pin 32 isaccepted in bores 22 and 30 for mating of adjacent links together. Pivotpin 32 is slidably received within bore 30 along its radial axis. Thisprovides for pivotal and sliding connection of adjacent links. Duringinsertion, this allows adjacent links to slide together, resulting incontact of flat faces 24, 26. This contact prevents buckling of links inthe straight part of tube 27. However, upon reaching a bend in tube 27,as illustrated in FIG. 1, sufficient lateral force from the tube bendcauses sliding of a link 12 relative to an adjacent link. This reducescontact between faces 24 and 26 and allows rotation of the link onrounded corners 28 to follow the bend of tube 27. Positioning spine 10may be designed to accomodate a variety of angles of tube bend byvarying the length of flattened end face 24.

To reduce drag during insertion and removal a wheel 14 is rotatablymounted on each pivot pin 32.

An alternate embodiment of the invention is illustrated in FIG. 4. It isseen that link 112 utilizes the same alignment and sliding features ofthe invention as described above. However, one of first or secondbifurcated ends 16, 18 is rotated about the longitudinal axis of link112 by 90 degrees relative to the other end. This accomodates bending intwo planes.

The alternate embodiment illustrated in FIG. 5 also accomodates bendingin two planes. Links 212 are provided with u-joints 40 at each end andalso utilize the same sliding features as described above to maintainstraightness during insertion in the straight part of the tube beinginspected. Each link is provided with a rectangular slot throughsubstantially its central portion, as indicated in phantom view by thevertical dotted lines, with a rectangular slot therethrough and acircular bore positioned at a ninety degree angle to the rectangularslot. A pin received in the circular bore extends through therectangular slot and has a wheel rotatably mounted thereon.

The alternate embodiment of FIG. 6 illustrates links 312 which utilizethe same sliding features as described above. Means for maintainingrigid straightness of the mated links when under compressive forces isprovided in the form of springs 44. Springs 44 are substantiallystraight springs formed from suitable material for such an applicationand are rigidly attached to the first bifurcated end of link 312 so asto extend over central link portion 20 of an adjacent link. At least twosprings 44 are provided, on opposite sides of first bifurcated end 16 toprovide straightening force from both bending directions. This providesa spring-loaded joint capable of bending as it travels through a tubebend but which returns to its normal straight position upon leaving thetube bend.

In operation, positioning spine 10 is attached to an inspection assembly34 which has one end similar to that of link 12 for proper mating andalignment. Inspection assembly 34 and positioning spine 10 are theninserted into tube 27 with the use of a driving mechanism, not shown,outside of tube 27. The sliding of links 12 together and contact of flatfaces 24,26 maintain straightness of positioning spine 10 in thestraight portions of tube 27. At tube bends lateral forces cause slidingof adjacent links which allows rotation on rounded corners 28 to followthe tube bend. After inspection of tube 27 is completed the direction ofthe driving mechanism is reversed and positioning spine 10 andinspection assembly 34 are removed. During removal the tension on theseparate links allows alignment of the links in conjunction with thegeometry of the tube. During insertion and removal wheels 14 reduce dragwhile rolling on the interior of tube 27. Positioning spine 10 may beformed from any suitable solid material. For purposes of economy,castables such as metal or plastic or molded parts of delrin arepreferred.

Because many varying and differing embodiments may be made within thescope of the inventive concept herein taught and because manymodifications may be made in the embodiment herein detailed inaccordance with the descriptive requirement of the law, it is to beunderstood that the details herein are to be interpreted as illustrativeand not in a limiting sense.

What is claimed as invention is:
 1. A positioning spine, comprising:a. aplurality of identical links; b. each link having a longitudinal axisand first and second bifurcated ends spaced along the axis and rotatedabout the longitudinal axis 90 degrees to each other in the form of aU-joint; c. said second bifurcated end having a substantially oval boretherethrough perpendicular to the longitudinal axis; d. said firstbifurcated end having a bore therethrough perpendicular to thelongitudinal axis; e. a U-joint drive pin accepted in said bores of saidfirst and second bifurcated ends of adjacent links for mating adjacentlinks together; f. means for maintaining rigid straightness of saidmated links when under longitudinal compressive forces comprising flatinner alignment faces on said second bifurcated end and correspondingflat end alignment faces on said first bifurcated end; and g. means forallowing pivoting of one link relative to an adjacent link.
 2. Thepositioning spine of claim 1, wherein said pivoting means comprises saidfirst bifurcated end having rounded corners.
 3. The positioning spine ofclaim 1, further comprising:a. each of said links having a rectangularslot through substantially the central portion of the link and acircular bore through the central portion of the link positioned at a 90degree angle to said rectangular slot; b. a pin received in saidcircular bore; and c. a wheel rotatably mounted on said pin.
 4. Apositioning spine, comprising:a. a plurality of identical links; b. eachlink having a longitudinal axis and first and second bifurcated endsspaced along the axis and rotated about the longitudinal axis 90 degreesto each other in the form of a U-joint; c. said first bifurcated endhaving a bore therethrough perpendicular to the longitudinal axis andhaving a flattened end face with rounded corners; d. said secondbifurcated end having a substantially oval bore therethroughperpendicular to the longitudinal axis and having flat inner alignmentfaces corresponding to said end face on said first bifurcated end; e. aU-joint drive pin accepted in said bores of said first and secondbifurcated ends of adjacent links for mating adjacent links together; f.each of said links having a rectangular slot through substantially thecentral portion of the link and a circular bore through the centralportion of the link positioned at a 90 degree angle to said rectangularslot; g. a pin received in said circular bore; and h. a wheel rotatablymounted on said pin.